use super::chunk::Chunk; use super::errors::{Error, ErrorKind, LoxResult}; use super::interner::{InternedStr, Interner}; use super::opcode::OpCode; use super::value::Value; use crate::scanner::{self, Token, TokenKind}; #[cfg(feature = "disassemble")] use super::chunk; struct Compiler> { tokens: T, chunk: Chunk, panic: bool, errors: Vec, strings: Interner, current: Option, previous: Option, } #[derive(Debug, PartialEq, PartialOrd)] enum Precedence { None, Assignment, // = Or, // or And, // and Equality, // == != Comparison, // < > <= >= Term, // + - Factor, // * / Unary, // ! - Call, // . () Primary, } type ParseFn = fn(&mut Compiler) -> LoxResult<()>; struct ParseRule> { prefix: Option>, infix: Option>, precedence: Precedence, } impl> ParseRule { fn new( prefix: Option>, infix: Option>, precedence: Precedence, ) -> Self { ParseRule { prefix, infix, precedence, } } } impl Precedence { // Return the next highest precedence, if there is one. fn next(&self) -> Self { match self { Precedence::None => Precedence::Assignment, Precedence::Assignment => Precedence::Or, Precedence::Or => Precedence::And, Precedence::And => Precedence::Equality, Precedence::Equality => Precedence::Comparison, Precedence::Comparison => Precedence::Term, Precedence::Term => Precedence::Factor, Precedence::Factor => Precedence::Unary, Precedence::Unary => Precedence::Call, Precedence::Call => Precedence::Primary, Precedence::Primary => panic!( "invalid parser state: no higher precedence than Primary" ), } } } fn rule_for>(token: &TokenKind) -> ParseRule { match token { TokenKind::LeftParen => { ParseRule::new(Some(Compiler::grouping), None, Precedence::None) } TokenKind::Minus => ParseRule::new( Some(Compiler::unary), Some(Compiler::binary), Precedence::Term, ), TokenKind::Plus => { ParseRule::new(None, Some(Compiler::binary), Precedence::Term) } TokenKind::Slash => { ParseRule::new(None, Some(Compiler::binary), Precedence::Factor) } TokenKind::Star => { ParseRule::new(None, Some(Compiler::binary), Precedence::Factor) } TokenKind::Number(_) => { ParseRule::new(Some(Compiler::number), None, Precedence::None) } TokenKind::True => { ParseRule::new(Some(Compiler::literal), None, Precedence::None) } TokenKind::False => { ParseRule::new(Some(Compiler::literal), None, Precedence::None) } TokenKind::Nil => { ParseRule::new(Some(Compiler::literal), None, Precedence::None) } TokenKind::Bang => { ParseRule::new(Some(Compiler::unary), None, Precedence::None) } TokenKind::BangEqual => { ParseRule::new(None, Some(Compiler::binary), Precedence::Equality) } TokenKind::EqualEqual => { ParseRule::new(None, Some(Compiler::binary), Precedence::Equality) } TokenKind::Greater => { ParseRule::new(None, Some(Compiler::binary), Precedence::Comparison) } TokenKind::GreaterEqual => { ParseRule::new(None, Some(Compiler::binary), Precedence::Comparison) } TokenKind::Less => { ParseRule::new(None, Some(Compiler::binary), Precedence::Comparison) } TokenKind::LessEqual => { ParseRule::new(None, Some(Compiler::binary), Precedence::Comparison) } TokenKind::String(_) => { ParseRule::new(Some(Compiler::string), None, Precedence::None) } _ => ParseRule::new(None, None, Precedence::None), } } macro_rules! consume { ( $self:ident, $expected:pat, $err:expr ) => { match $self.current().kind { $expected => $self.advance(), _ => $self.error_at($self.current().line, $err), } }; } impl> Compiler { fn compile(&mut self) -> LoxResult<()> { self.advance(); while !self.match_token(&TokenKind::Eof) { self.declaration()?; } self.end_compiler() } fn advance(&mut self) { self.previous = self.current.take(); self.current = self.tokens.next(); } fn expression(&mut self) -> LoxResult<()> { self.parse_precedence(Precedence::Assignment) } fn var_declaration(&mut self) -> LoxResult<()> { let global = self.parse_variable()?; if self.match_token(&TokenKind::Equal) { self.expression()?; } else { self.emit_op(OpCode::OpNil); } self.expect_semicolon("expect ';' after variable declaration")?; self.define_variable(global) } fn define_variable(&mut self, var: usize) -> LoxResult<()> { self.emit_op(OpCode::OpDefineGlobal(var)); Ok(()) } fn declaration(&mut self) -> LoxResult<()> { if self.match_token(&TokenKind::Var) { self.var_declaration()?; } else { self.statement()?; } if self.panic { self.synchronise(); } Ok(()) } fn statement(&mut self) -> LoxResult<()> { if self.match_token(&TokenKind::Print) { self.print_statement() } else { self.expression_statement() } } fn print_statement(&mut self) -> LoxResult<()> { self.expression()?; self.expect_semicolon("expect ';' after print statement")?; self.emit_op(OpCode::OpPrint); Ok(()) } fn expression_statement(&mut self) -> LoxResult<()> { self.expression()?; self.expect_semicolon("expect ';' after expression")?; self.emit_op(OpCode::OpPop); Ok(()) } fn number(&mut self) -> LoxResult<()> { if let TokenKind::Number(num) = self.previous().kind { self.emit_constant(Value::Number(num)); return Ok(()); } unreachable!("internal parser error: entered number() incorrectly") } fn grouping(&mut self) -> LoxResult<()> { self.expression()?; consume!( self, TokenKind::RightParen, ErrorKind::ExpectedToken("Expected ')' after expression") ); Ok(()) } fn unary(&mut self) -> LoxResult<()> { // TODO(tazjin): Avoid clone let kind = self.previous().kind.clone(); // Compile the operand self.parse_precedence(Precedence::Unary)?; // Emit operator instruction match kind { TokenKind::Bang => self.emit_op(OpCode::OpNot), TokenKind::Minus => self.emit_op(OpCode::OpNegate), _ => unreachable!("only called for unary operator tokens"), } Ok(()) } fn binary(&mut self) -> LoxResult<()> { // Remember the operator let operator = self.previous().kind.clone(); // Compile the right operand let rule: ParseRule = rule_for(&operator); self.parse_precedence(rule.precedence.next())?; // Emit operator instruction match operator { TokenKind::Minus => self.emit_op(OpCode::OpSubtract), TokenKind::Plus => self.emit_op(OpCode::OpAdd), TokenKind::Star => self.emit_op(OpCode::OpMultiply), TokenKind::Slash => self.emit_op(OpCode::OpDivide), TokenKind::BangEqual => { self.emit_op(OpCode::OpEqual); self.emit_op(OpCode::OpNot); } TokenKind::EqualEqual => self.emit_op(OpCode::OpEqual), TokenKind::Greater => self.emit_op(OpCode::OpGreater), TokenKind::GreaterEqual => { self.emit_op(OpCode::OpLess); self.emit_op(OpCode::OpNot); } TokenKind::Less => self.emit_op(OpCode::OpLess), TokenKind::LessEqual => { self.emit_op(OpCode::OpGreater); self.emit_op(OpCode::OpNot); } _ => unreachable!("only called for binary operator tokens"), } Ok(()) } fn literal(&mut self) -> LoxResult<()> { match self.previous().kind { TokenKind::Nil => self.emit_op(OpCode::OpNil), TokenKind::True => self.emit_op(OpCode::OpTrue), TokenKind::False => self.emit_op(OpCode::OpFalse), _ => unreachable!("only called for literal value tokens"), } Ok(()) } fn string(&mut self) -> LoxResult<()> { let val = match &self.previous().kind { TokenKind::String(s) => s.clone(), _ => unreachable!("only called for strings"), }; let id = self.strings.intern(val); self.emit_constant(Value::String(id.into())); Ok(()) } fn parse_precedence(&mut self, precedence: Precedence) -> LoxResult<()> { self.advance(); let rule: ParseRule = rule_for(&self.previous().kind); let prefix_fn = match rule.prefix { None => unimplemented!("expected expression or something, unclear"), Some(func) => func, }; prefix_fn(self)?; while precedence <= rule_for::(&self.current().kind).precedence { self.advance(); match rule_for::(&self.previous().kind).infix { Some(func) => { func(self)?; } None => { unreachable!("invalid compiler state: error in parse rules") } } } Ok(()) } fn identifier_str( &mut self, token_fn: fn(&Self) -> &Token, ) -> LoxResult { let ident = match &token_fn(self).kind { TokenKind::Identifier(ident) => ident.to_string(), _ => { return Err(Error { line: self.current().line, kind: ErrorKind::ExpectedToken("Expected identifier"), }) } }; Ok(self.strings.intern(ident)) } fn parse_variable(&mut self) -> LoxResult { consume!( self, TokenKind::Identifier(_), ErrorKind::ExpectedToken("expected identifier") ); let id = self.identifier_str(Self::previous)?; Ok(self.emit_constant(Value::String(id.into()))) } fn current_chunk(&mut self) -> &mut Chunk { &mut self.chunk } fn end_compiler(&mut self) -> LoxResult<()> { self.emit_op(OpCode::OpReturn); #[cfg(feature = "disassemble")] { chunk::disassemble_chunk(&self.chunk); println!("== compilation finished =="); } Ok(()) } fn emit_op(&mut self, op: OpCode) { let line = self.previous().line; self.current_chunk().add_op(op, line); } fn emit_constant(&mut self, val: Value) -> usize { let idx = self.chunk.add_constant(val); self.emit_op(OpCode::OpConstant(idx)); idx } fn previous(&self) -> &Token { self.previous .as_ref() .expect("invalid internal compiler state: missing previous token") } fn current(&self) -> &Token { self.current .as_ref() .expect("invalid internal compiler state: missing current token") } fn error_at(&mut self, line: usize, kind: ErrorKind) { if self.panic { return; } self.panic = true; self.errors.push(Error { kind, line }) } fn match_token(&mut self, token: &TokenKind) -> bool { if !self.check(token) { return false; } self.advance(); true } fn check(&self, token: &TokenKind) -> bool { return self.current().kind == *token; } fn synchronise(&mut self) { self.panic = false; while self.current().kind != TokenKind::Eof { if self.previous().kind == TokenKind::Semicolon { return; } match self.current().kind { TokenKind::Class | TokenKind::Fun | TokenKind::Var | TokenKind::For | TokenKind::If | TokenKind::While | TokenKind::Print | TokenKind::Return => return, _ => { self.advance(); } } } } fn expect_semicolon(&mut self, msg: &'static str) -> LoxResult<()> { consume!(self, TokenKind::Semicolon, ErrorKind::ExpectedToken(msg)); Ok(()) } } pub fn compile(code: &str) -> Result<(Interner, Chunk), Vec> { let chars = code.chars().collect::>(); let tokens = scanner::scan(&chars).map_err(|errors| { errors.into_iter().map(Into::into).collect::>() })?; let mut compiler = Compiler { tokens: tokens.into_iter().peekable(), chunk: Default::default(), panic: false, errors: vec![], strings: Interner::with_capacity(1024), current: None, previous: None, }; compiler.compile()?; if compiler.errors.is_empty() { Ok((compiler.strings, compiler.chunk)) } else { Err(compiler.errors) } }